Community colleges should replace weak remedial programs with innovative practices as a way to increase completion rates, Melinda F. Gates, co-chairman of the Bill & Melinda Gates Foundation, told two-year college leaders Tuesday as she delivered the closing speech here at the American Association of Community Colleges’ annual meeting.

To that end, Ms. Gates said that her foundation is spending up to $110-million to work with dozens of partners, including colleges and school districts, to develop groundbreaking models for remedial education and to replicate effective practices. About half of the foundation’s commitment has already been given to colleges and programs. The remaining $57-million will be given as grants over the next two years.

Ms. Gates called traditional remedial programs “an afterthought” on most campuses. Such low-quality programs, designed to help students catch up academically, are actually the biggest obstacles students must overcome in their pursuit of a college degree, she said.

“Our research indicates that improving remediation is the single most important thing community colleges can do to increase the number of students who graduate,” Ms. Gates said.

Community colleges can either “keep doing what you’ve been doing, in which case you will gradually find yourself able to meet fewer and fewer of your students’ needs, or you can innovate,” she said. “You can educate your students according to new models that yield dramatically better results for a fraction of the cost.”

She said community colleges have led the way on college access and that it is now time for them to lead the way on college completion.

As many as 60 percent of students enrolled in community colleges must take at least one remedial course. But only about 25 percent of all students who take those courses earn a degree within eight years of enrolling.